The Effects of Wortmannin on Rat Skeletal Muscle

Yeh, Jih‐I; Gulve, E. A.; Rameh, Lucia E.; Birnbaum, Morris J.

doi:10.1074/jbc.270.5.2107

Cited by 282 publications

(134 citation statements)

References 30 publications

Supporting

Mentioning

118

Contrasting

Order By: Relevance

“…The ED 50 for this effect is around 100 nmol/l which is an order of magnitude higher than insulin's inhibitory effects on glucose transport in isolated adipocytes and cell culture models [9,10]. Similar observations have been made in rodent muscle where 100 nmol/l wortmannin is insufficient to completely block insulin stimulation of glucose uptake into rat muscle [28,29]. The reason for this is not clear but wortmannin is known to be labile and the differences in efficacy could be due to increased degradation of wortmannin in muscle.…”

Section: Discussionmentioning

confidence: 71%

Involvement of phosphoinositide 3-kinase in insulin stimulation of MAP-kinase and phosphorylation of protein kinase-B in human skeletal muscle: implications for glucose metabolism

et al. 1997

View full text Add to dashboard Cite

Insulin binding to its cell surface receptor activates a range of intracellular signalling cascades that ultimately result in the regulation of a number of important metabolic events within the cell [1]. Of particular importance is insulin stimulation of glucose transport and stimulation of glycogen deposition in muscle as this accounts for the bulk of insulin stimulated glucose disposal from the blood [2,3]. Peripheral insulin resistance at the level of skeletal muscle plays an important role in the development of hyperinsulinaemia and hyperglycaemia associated with obesity [4] and non-insulin-dependent diabetes [5]. The consensus of opinion is that defects in insulin signalling lead to the reduced ability of insulin to stimulate glucose disposal into muscle in insulin resistant individuals [6,7]. Understanding the molecular mechanisms by which insulin regulates glucose transport and glycogen storage in skeletal muscle is therefore of great importance. Insulin acutely stimulates phosphoinositide-3 (PI 3)-kinase and evidence suggests that PI 3-kinase activity is necessary [8][9][10] and sufficient [11,12] for insulin stimulation of glucose transport and also necessary for insulin activation of glycogen synthase [13,14]. Further, there is evidence to suggest that protein kinase B (PKB) is an element of the signalling cascade leading from PI 3-kinase to activation of glycogen synthase in cell culture models [15,16]. Insulin's regulation of these pathways has not been investigated in intact human skeletal muscle. Diabetologia (1997) Summary Isolated skeletal muscle from healthy individuals was used to evaluate the role of phosphoinositide 3-kinase (PI 3-kinase) in insulin signalling pathways regulating mitogen activated protein kinase (MAP-kinase) and protein kinase-B and to investigate whether MAP-kinase was involved in signalling pathways regulating glucose metabolism. Insulin stimulated glycogen synthase activity ( ≈ 1.7 fold), increased 3-o-methylglucose transport into human skeletal muscle strips ( ≈ 2 fold) and stimulated phosphorylation of the p42 ERK-2 isoform of MAP-kinase. This phosphorylation of p42 ERK2 was not blocked by the PI 3-kinase inhibitors LY294002 and wortmannin although it was blocked by the MAPkinase kinase (MEK) inhibitor PD 98059. However, PD98059 (up to 20 m mol/l) did not block insulin activation of glycogen synthase or stimulation of 3-o-methylglucose transport. Wortmannin and LY294002 did block insulin stimulation of protein kinase-B (PKB) phosphorylation and stimulation of 3-o-methylglucose transport was inhibited by wortmannin (IC 50 ≈ 100 nmol/l). These results indicate that MAP-kinase is activated by insulin in human skeletal muscle by a PI 3-kinase independent pathway. Furthermore this activation is not necessary for insulin stimulation of glucose transport or activation of glycogen synthase in this tissue.

show abstract

Section: Discussionmentioning

confidence: 71%

Involvement of phosphoinositide 3-kinase in insulin stimulation of MAP-kinase and phosphorylation of protein kinase-B in human skeletal muscle: implications for glucose metabolism

et al. 1997

View full text Add to dashboard Cite

show abstract

“…We recently demonstrated (Zawalich & Zawalich 2000) that the fungal metabolite wortmannin, a specific PI3K inhibitor at nanomolar concentrations (Acaro & Wymann 1993, Okada et al 1994, Yeh et al 1995, amplified 8 mM glucose-induced insulin secretion from perifused rat islets. Since PI3K activation by insulin receptor substrate proteins appears to determine liver, muscle and adipose tissue sensitivity to insulin, we suggested that this signaling pathway might provide a means for the -cell to monitor insulin sensitivity in peripheral tissues and to adjust their secretory responses accordingly.…”

Section: Introductionmentioning

confidence: 90%

Inhibitors of phosphatidylinositol 3-kinase amplify insulin release from islets of lean but not obese mice

Zawalich

Tesz²,

Zawalich³

2002

Journal of Endocrinology

View full text Add to dashboard Cite

We examined the effects of phosphatidylinositol 3-kinase (PI3K) inhibition by wortmannin or LY294002 on glucose-induced secretion from mouse islets. Islets were collagenase isolated and perifused or subjected to Western blot analyses and probed for insulin receptor-signaling components. In agreement with previous studies, mouse islets, when compared with rat islets, were minimally responsive to 10 mM glucose stimulation. The inclusion of 50 nM wortmannin or 10 µM LY294002 significantly amplified 10 mM glucose-induced release from mouse islets. The effect of wortmannin was abolished by the calcium channel antagonist nitrendipine or by lowering the glucose level to 3 mM. Wortmannin had no effect on 10 mM -ketoisocaproate-induced secretion. In contrast to its potentiating effect on islets from CD-1 mice, wortmannin had no effect on 10 mM glucose-induced release from ob/ob mouse islets. Western blot analyses revealed the presence of the insulin receptor, insulin receptor substrate proteins 1 and 2 and PI3K in CD-1 islets. These results support the concept that a PI3K-dependent signaling pathway exists in -cells and that it may function to restrain glucose-induced insulin secretion from -cells. They also suggest that, as insulin resistance develops in peripheral tissues, a potential result of impaired PI3K activation, the same biochemical anomaly in -cells promotes a linked increase in insulin secretion to maintain glucose homeostasis.

show abstract

“…Two distinct signalling cascades operate in skeletal muscle to stimulate glucose utilization, namely the insulin-and contractionmediated pathways [1,2]. Neither cascade has been fully characterized at the molecular level.…”

Section: Introductionmentioning

confidence: 99%

Evidence for altered sensitivity of the nitric oxide/cGMP signalling cascade in insulin-resistant skeletal muscle

Young

Leighton

1998

Biochemical Journal

View full text Add to dashboard Cite

Nitric oxide activates guanylate cyclase to form cGMP, comprising a signalling system that is believed to be a distinct mechanism for increasing glucose transport and metabolism in skeletal muscle. The effects of a selective cGMP phosphodiesterase inhibitor, zaprinast, on basal glucose utilization was investigated in incubated rat soleus muscle preparations isolated from both insulin-sensitive (lean Zucker; Fa/?) and insulin-resistant (obese Zucker; fa/fa) rats. Zaprinast at 27 μM significantly increased cGMP levels in incubated soleus muscle isolated from lean, but not obese, Zucker rats. Muscles were incubated with 14C-labelled glucose and various concentrations of zaprinast (3, 27 and 243 μM). Zaprinast (at 27 and 243 μM) significantly increased rates of net and 14C-labelled lactate release and of glycogen synthesis in lean Zucker rat soleus muscle; glucose oxidation was also increased by 27 μM zaprinast. In addition, regardless of concentration, the phosphodiesterase inhibitor failed to increase any aspect of 14C-labelled glucose utilization in soleus muscles isolated from obese Zucker rats. The maximal activity of nitric oxide synthase (NOS) was significantly decreased in insulin-resistant obese Zucker muscles. Thus the lack of effect of zaprinast in insulin-resistant skeletal muscle is consistent with decreased NOS activity. To test whether there is a defect in insulin-resistant skeletal muscle for endogenous activation of guanylate cyclase, soleus muscles were isolated from both insulin-sensitive and insulin-resistant Zucker rats and incubated with various concentrations of the NO donor sodium nitroprusside (SNP; 0.1, 1, 5 and 15 mM). SNP significantly increased rates of net and 14C-labelled lactate release, as well as glucose oxidation in muscles isolated from both insulin-sensitive and insulin-resistant rats. A decreased response to SNP was observed in the dose-dependent generation of cGMP within isolated soleus muscles from insulin-resistant rats. A possible link between impaired NO/cGMP signalling and abnormal glucose utilization by skeletal muscle is discussed.

show abstract

The Effects of Wortmannin on Rat Skeletal Muscle

Cited by 282 publications

References 30 publications

Involvement of phosphoinositide 3-kinase in insulin stimulation of MAP-kinase and phosphorylation of protein kinase-B in human skeletal muscle: implications for glucose metabolism

Involvement of phosphoinositide 3-kinase in insulin stimulation of MAP-kinase and phosphorylation of protein kinase-B in human skeletal muscle: implications for glucose metabolism

Inhibitors of phosphatidylinositol 3-kinase amplify insulin release from islets of lean but not obese mice

Evidence for altered sensitivity of the nitric oxide/cGMP signalling cascade in insulin-resistant skeletal muscle

Contact Info

Product

Resources

About